Rotor assembly and motor including the same

ABSTRACT

A rotor assembly includes a shaft with a central axis extending along an up and down direction as a center, and a cylindrical rotor main body fixed to an outer surface of the shaft, and the rotor main body includes core pieces arranged around the shaft in a circumferential direction, rotor magnets alternately arranged with the core pieces around the shaft in the circumferential direction, and a connection portion made of resin and connecting the shaft to the core pieces and the rotor magnets. Each of the rotor magnets includes an engagement region covered by the connection portion of the rotor magnet surface, and an exposed region including an outer surface positioned outward of the rotor magnet surface in a radial direction and is exposed from the connection portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese PatentApplication No. 2017-155390 filed on Aug. 10, 2017. The entire contentsof this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a rotor assembly of a motor.

2. Description of the Related Art

In the related art, an inner rotor type motor in which a rotor isdisposed inward of a stator in a radial direction is known. In themotor, in a rotor, a large number of core pieces and magnets arealternately disposed in a circumferential direction.

In the rotor, a stopper protrusion which protrudes in thecircumferential direction toward the magnet from an end portion of thecore piece in the radial direction is provided in order to prevent themagnet from separating in the radial direction. The stopper protrusionis positioned outside an outer surface of the magnet in the radialdirection and covers an end portion of the outer surface of the magnetin the circumferential direction. Accordingly, outward movement of themagnet in the radial direction is suppressed.

Incidentally, in the motor, since the stopper protrusion of a core pieceis disposed outward of the outer surface of the magnet in the radialdirection, there is a possibility that the rotor becomes large in theradial direction. In addition, since the radial distance between theouter surface of the magnet and the stator increases, there is apossibility that leakage magnetic flux increases and output of the motormay decrease.

SUMMARY OF THE INVENTION

A preferred embodiment of the present disclosure provides a rotorassembly including: a shaft which has a central axis along an up anddown direction as a center; and a cylindrical rotor main body which isfixed to an outer surface of the shaft. The rotor main body includescore pieces which are arranged around the shaft in a circumferentialdirection, rotor magnets which are alternately arranged with the corepieces around the shaft in the circumferential direction, and aconnection portion which is made of resin and connects the shaft to thecore pieces and the rotor magnets. Each of the rotor magnets includes anengagement region which is covered by the connection portion of therotor magnet surface, and an exposed region which includes an outersurface positioned outward of the rotor magnet surface in a radialdirection and is exposed out from the connection portion. The engagementregion includes an engagement surface which has a component whose normalvector faces outward in the radial direction.

The above and other elements, features, steps, characteristics, andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating a motor according to a preferredembodiment of the present invention.

FIG. 2 is a perspective view illustrating an internal structure of themotor.

FIG. 3 is a transverse sectional view illustrating the motor.

FIG. 4 is a longitudinal sectional view illustrating the motor.

FIG. 5 is a perspective view illustrating the internal structure of themotor by omitting a connection portion.

FIG. 6 is a longitudinal sectional view illustrating a rotor magnetaccording to a preferred embodiment of the present invention.

FIG. 7 is a transverse sectional view illustrating of the rotor magnet.

FIG. 8 is a view illustrating a flow of manufacturing a rotor assemblyaccording to a preferred embodiment of the present invention.

FIG. 9 is a transverse sectional view illustrating the rotor assembly inthe course of manufacture.

FIG. 10 is a longitudinal sectional view illustrating a rotor assemblyin the course of manufacture.

FIG. 11 is a longitudinal sectional view illustrating another rotormagnet according to a preferred embodiment of the present invention.

FIG. 12 is a transverse sectional view illustrating another rotor magnetaccording to a preferred embodiment of the present invention.

FIG. 13 is a transverse sectional view illustrating a rotor magnet of arotor assembly according to another preferred embodiment of the presentinvention.

FIG. 14 is a longitudinal sectional view of another motor according to apreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a side view illustrating an outer appearance of a motor 1according to a preferred embodiment of the present invention. The motor1 is an inner rotor type brushless motor. The motor 1 is used, forexample, to rotate an impeller in an axial flow fan. FIG. 2 is aperspective view illustrating an internal structure of the motor 1. InFIG. 2, a portion of the housing 21 or the like of the motor 1 isomitted for illustration. FIG. 3 is a transverse sectional view of themotor 1. FIG. 4 is a longitudinal sectional view of the motor 1 cut atposition IV-IV in FIG. 3. In FIG. 3 and FIG. 4, parallel slanted linesin the detailed cross section are omitted.

In this specification, an upper side in a direction of a central axis J1of the motor 1 in FIG. 4 is simply referred to as “upper side”, and alower side is simply referred to as “lower side”. The upper side and thelower side in this specification do not indicate the upper side and thelower side in the direction of gravity when incorporated in actualequipment.

In the following description, a circumferential direction which has thecentral axis J1 as a center is simply referred to as “circumferentialdirection”, and the radial direction which has the central axis J1 as acenter is simply referred to as “radial direction”. In addition, thedirection parallel to the central axis J1 is referred to as “up and downdirection”. The up and down direction is also an axial direction.

The motor 1 includes a stationary portion 2, a rotation portion 3, and abearing mechanism 4. The bearing mechanism 4 rotatably supports therotation portion 3 with respect to the stationary portion 2. Thestationary portion 2 includes a housing 21, an armature 22, a bus bar23, and a bus bar holding portion 24. The rotation portion 3 includes arotor assembly 30 and a rotor fan 34. The rotor assembly 30 includes ashaft 31, a rotor main body 32, and a connection plate portion 33. Thebearing mechanism 4 includes a first bearing 41 and a second bearing 42.The first bearing 41 and the second bearing 42 are, for example, ballbearings.

The housing 21 is a substantially cylindrical member having a bottom anda lid, which has the central axis J1 along the up and down direction asa center. The housing 21 includes a side wall portion 211, a bottomportion 212, and a canopy portion 213. The side wall portion 211 is asubstantially cylindrical portion which has the central axis J1 as acenter. The bottom portion 212 is a substantially annular plate-shapedportion which has the central axis J1 as a center. The bottom portion212 is connected to the lower end portion of the side wall portion 211and covers a lower opening of the side wall portion 211. The canopyportion 213 is a substantially disk-like portion which has the centralaxis J1 as a center. The canopy portion 213 is connected to an upper endportion of the side wall portion 211 and covers the upper opening of theside wall portion 211.

In the housing 21, a plurality of first openings 215 are provided in anupper portion of the side wall portion 211. In an example illustrated inFIG. 1, four first openings 215 are positioned on the outer surface ofthe housing 21. The plurality of first openings 215 are arranged atsubstantially equal angular intervals in the circumferential directionat substantially the same position in the up and down direction. Theplurality of first openings 215 are positioned above the armature 22.Each first opening 215 is a through hole penetrating the side wallportion 211 in the radial direction. Each of the first openings 215 is asubstantially rectangular shape extending in the circumferentialdirection in a side view. The shape of the first opening 215 may beappropriately changed. The number of the first openings 215 may be 1, or2 or more.

In addition, in the housing 21, a plurality of second openings 216 areprovided in the outer peripheral portion of the bottom portion 212. Theplurality of second openings 216 are positioned below the armature 22.The plurality of second openings 216 are arranged at substantially equalangular intervals in the circumferential direction at substantially thesame position in the radial direction. Each second opening 216 is athrough hole penetrating the bottom portion 212 in the up and downdirection. Each of the second openings 216 is a substantiallyrectangular shape in a plan view. The shape of the second opening 216may be appropriately changed. The number of the second openings 216 maybe 1, or 2 or more. In an example illustrated in FIG. 2, twelve secondopenings 216 which are equal in number to the teeth 222 (describedbelow) of the armature 22 are positioned between the plurality of teeth222 in the circumferential direction in the bottom surface of thehousing 21.

The upper portion of the shaft 31, the rotor main body 32, the rotor fan34, the armature 22, the bus bar 23, and the bus bar holding portion 24are accommodated in the housing 21. The lower end portion of the shaft31 protrudes downward from the bottom portion 212 of the housing 21. Atthe lower end portion of the shaft 31, for example, the impeller of anaxial flow fan is attached.

The shaft 31 is a substantially columnar or substantially cylindricalmember which has the central axis J1 as a center. In an exampleillustrated in FIG. 4, the shaft 31 is a substantially cylindricalmember. Accordingly, it is possible to reduce the weight of the shaft 31and the motor 1. The shaft 31 is, for example, a member made of anon-magnetic material. The shaft 31 is formed of, for example, stainlesssteel. The shaft 31 is rotatably supported by the bearing mechanism 4.

The first bearing 41 of the bearing mechanism 4 rotatably supports theupper end portion of the shaft 31 at the upper end portion in thehousing 21. The first bearing 41 is a substantially cylindrical memberwhich has the central axis J1 as a center. In the example illustrated inFIG. 4, the first bearing 41 is held by a bearing holding portion 214 ofthe housing 21. The bearing holding portion 214 is a substantiallycylindrical portion protruding downward from the canopy portion 213 ofthe housing 21 toward the inside of the housing 21. The bearing holdingportion 214 is in contact with the outer surface of the first bearing 41and holds the first bearing 41.

The second bearing 42 of the bearing mechanism 4 is positioned below thefirst bearing 41 and rotatably supports the lower portion of the shaft31. The second bearing 42 is positioned, for example, below the rotormain body 32. The second bearing 42 is a substantially cylindricalmember which has the central axis J1 as a center. The outer diameter ofthe second bearing 42 is, for example, smaller than the outer diameterof the first bearing 41. In the example illustrated in FIG. 4, thesecond bearing 42 is positioned substantially at the same position asthe bottom portion 212 of the housing 21 in the up and down direction.The second bearing 42 is held by the bottom portion 212 of the housing21.

The rotor main body 32 is a substantially cylindrical member which hasthe central axis J1 as a center. The rotor main body 32 is fixed to theouter surface of the shaft 31. The rotor main body 32 is fixed to theshaft 31 by insert molding, for example. At both ends of the rotor mainbody 32 in the up and down direction, a substantially annular plate-likeconnection plate portion 33 is disposed. The rotor main body 32 is alsoconnected to the shaft 31 by the connection plate portion 33. Theconnection plate portion 33 may be provided only at one of the upper endportion and the lower end portion of the rotor main body 32.

The rotor main body 32 includes a plurality of core pieces 321, aplurality of rotor magnets 322, and a connection portion 323. Theplurality of core pieces 321 are made of magnetic metal. Each core piece321 is formed by stacking in the up and down direction and caulking aplate member made of a magnetic metal such as a steel plate. Theconnection portion 323 is made of resin.

The plurality of core pieces 321 are arranged around the shaft 31 in thecircumferential direction. The plurality of rotor magnets 322 arearranged alternately with the plurality of core pieces 321 around theshaft 31 in the circumferential direction. The plurality of core pieces321 are disposed at substantially equal angular intervals. The pluralityof rotor magnets 322 are also arranged at substantially equal angularintervals. In an example illustrated in FIG. 3, fourteen core pieces 321and fourteen rotor magnets 322 are alternately arranged in thecircumferential direction.

In the plan view, each core piece 321 is a portion of the substantiallyannular shape in the circumferential direction which has the centralaxis J1 as a center. Each rotor magnet 322 has a substantiallyrectangular shape extending along the radial direction in the plan view.The plan view is a shape of the object viewed from the upper side with aview line parallel to the central axis J1. The width of the outersurface of each core piece 321 in the circumferential direction is, forexample, larger than the width of the outer surface of each rotor magnet322 in the circumferential direction. The shapes of the core piece 321and the rotor magnet 322 may be variously changed. The number of thecore piece 321 and the rotor magnet 322 may be appropriately changedwithin a range of 2 or more, respectively.

In the rotor main body 32, a substantially cylindrical assembly isformed by the plurality of core pieces 321 and the plurality of rotormagnets 322. The outer surfaces of the plurality of core pieces 321 andthe outer surfaces of the plurality of rotor magnets 322 are positionedat substantially the same position in the radial direction. In otherwords, the distance between the central axis J1 and the outer surface ofeach core piece 321 in the radial direction and the distance between thecentral axis J1 and the outer surface of each rotor magnet 322 in theradial direction are substantially the same. Accordingly, the leakagemagnetic flux from the rotor magnet 322 can be reduced and the output ofthe motor 1 can increase. In addition, the inner ends of the pluralityof rotor magnets 322 in the radial direction are closer to the shaft 31than the inner ends of the plurality of core pieces 321 in the radialdirection. In other words, the distance between the inner end in theradial direction of each rotor magnet 322 and the shaft 31 in the radialdirection is smaller than the distance between the inner end in theradial direction of each core piece 321 and the shaft 31 in the radialdirection. In other words, the inner ends of the plurality of rotormagnets 322 in the radial direction protrude inward from the innersurfaces of the plurality of core pieces 321 in the radial direction.

The upper end of each core piece 321 is positioned below the upper endof each rotor magnet 322. The lower end of each core piece 321 ispositioned above the lower end of each rotor magnet 322. In other words,the upper end portion and the lower end portion of the plurality ofrotor magnets 322 protrude from the upper end and the lower end of theplurality of core pieces 321 in the up and down direction.

The connection portion 323 is a substantially cylindrical portion whichhas the central axis J1 as a center. The connection portion 323 connectsthe shaft 31 to the plurality of core pieces 321 and the plurality ofrotor magnets 322. The connection portion 323 is formed by filling aspace between the shaft 31 and the plurality of core pieces 321 and theplurality of rotor magnets 322 with resin. In other words, theconnection portion 323 fills the space between the shaft 31 and theplurality of core pieces 321 and the plurality of rotor magnets 322.

At the central portion of the upper end surface of the connectionportion 323, a central protrusion portion 326 protruding upward from aregion around the upper end surface is provided. The central protrusionportion 326 is a substantially cylindrical portion in contact with theouter surface of the shaft 31. The outer surface of the centralprotrusion portion 326 is an inclined surface facing inward in theradial direction as the outer surface thereof goes upward.

The connection portion 323 covers an outer surface of the shaft 31, aninner surface positioned inward of the surface of each of the respectivecore pieces 321 in the radial direction, an inner surface positionedinward of the surface of the rotor magnet 322 in the radial direction,and the inner end portions in the radial direction of both side surfacesof each of the rotor magnet 322 in the circumferential direction. A corerecessed portion 324 recessed outward in the radial direction isprovided on the inner surface of each core piece 321. In the vicinity ofthe inner surface of the core piece 321, the width of the core recessedportion 324 in the circumferential direction gradually increases as thecore recessed portion goes farther outward from the inner surface of thecore piece 321 in the radial direction. The maximum width of the corerecessed portion 324 in the circumferential direction is larger than thewidth of the core recessed portion 324 in the circumferential directionon the inner surface of the core piece 321.

In the core recessed portion 324, the resin of the connection portion323 is present. A portion of the connection portion 323 positioned inthe core recessed portion 324 and a portion of the connection portion323 positioned inward of the inner surface of the core piece 321 in theradial direction are continuous resin members which are connected toeach other via the opening at the inner end of the core recessed portion324 in the radial direction. The connection portion 323 also covers bothend surfaces of the plurality of core pieces 321 and the plurality ofrotor magnets 322 in the up and down direction.

FIG. 5 is a perspective view of the motor 1 in which the connectionportion 323 of FIG. 2 is not illustrated. Each connection plate portion33 includes a first portion 331 and a plurality of second portions 332.The first portion 331 has a substantially annular shape which has thecentral axis J1 as a center. The plurality of second portions 332 extendradially outward from the outer peripheral edge of the first portion 331in the radial direction. The plurality of second portions 332 arearranged at substantially equal angular intervals in the circumferentialdirection. The number of the plurality of second portions 332 is thesame as the number of the plurality of core pieces 321. The shape ofeach second portion 332 in the plan view is substantially the same asthe shape of the core piece 321 in the plan view.

The first portion 331 of the connection plate portion 33 is connected tothe outer surface of the shaft 31 by press fitting or the like. Theplurality of second portions 332 overlap the plurality of core pieces321 in the up and down direction. Both end surfaces of each core piece321 in the up and down direction are covered by the second portion 332of the connection plate portion 33. The plurality of second portions 332come in contact with the end surfaces of the plurality of core pieces321 in the up and down direction and are connected to the plurality ofcore pieces 321. Accordingly, the plurality of core pieces 321 of therotor main body 32 and the shaft 31 are connected, and the plurality ofcore pieces 321 are prevented from shifting with respect to the shaft 31in the circumferential direction. The connection plate portion 33 andthe plurality of core pieces 321 are connected to each other byinserting pins protruding from the end surfaces of the respective corepieces 321 in the up and down direction into the holes provided in therespective second portions 332 of the connection plate portion 33. Inthe example illustrated in FIG. 4, among the two connection plateportions 33, only the lower connection plate portion 33 is directlyconnected to the outer surface of the shaft 31, and the upper connectionplate portion 33 is slightly spaced from the outer surface of the shaft31.

Both end surfaces of the plurality of rotor magnets 322 in the up anddown direction are positioned between the plurality of second portions332 in the circumferential direction. In other words, both end surfacesof each rotor magnet 322 in the up and down direction are notsubstantially covered by the connection plate portion 33, but areexposed from between the two second portions 332 adjacent in thecircumferential direction. The upper end of each rotor magnet 322 ispositioned at substantially the same position in the up and downdirection as the upper end surface of each second portion 332 of theupper connection plate portion 33. The lower end of each rotor magnet322 is positioned at substantially the same position in the up and downdirection as the lower end surface of each second portion 332 of thelower connection plate portion 33.

As illustrated in FIGS. 2 and 4, the connection portion 323 of the rotormain body 32 covers the both end surfaces of a plurality of core pieces321 and a plurality of rotor magnets 322 from above the connection plateportion 33 on both sides of the plurality of core pieces 321 and theplurality of rotor magnets 322 in the up and down direction. Since theend surface of each core piece 321 in the up and down direction iscovered by the connection plate portion 33 as described above, theconnection portion 323 indirectly come in contact with the end surfaceof each core piece 321 in the up and down direction via the connectionplate portion 33. In addition, the connection portion 323 directly comein contact with the end surfaces of each of the rotor magnets 322 in theup and down direction without going via the connection plate portion 33.

FIG. 6 is an enlarged longitudinal transverse sectional viewillustrating one rotor magnet 322 and vicinity thereof. In addition, inFIG. 6, a core piece 321 adjacent to the rotor magnet 322 is indicatedby a two-dot chain line. FIG. 7 is an enlarged transverse sectional viewillustrating the rotor magnet 322 and vicinity thereof. The shapes andstructures of other rotor magnets 322 and vicinities thereof aresubstantially the same as those illustrated in FIGS. 6 and 7.

Among the surfaces of the rotor magnet 322, the upper end surface 351and the lower end surface 352 are covered by the connection portion 323over substantially the entire surface. In addition, among the surfacesof the rotor magnet 322, the inner surface 361 positioned inward in theradial direction is also covered by the connection portion 323 oversubstantially the entire surface. On the side surfaces 362 on both sidesof the rotor magnet 322 in the circumferential direction, the region 365of the inner end in the radial direction continuous from the innersurface 361 is covered by the connection portion 323, and the regionother than the region 365 is covered by the adjacent core piece 321 inthe circumferential direction. In the following description, the region365 is referred to as “side surface inner end region 365”. The outersurface 363 of the surfaces of rotor magnet 322 positioned outward inthe radial direction is not covered by the connection portion 323, thecore piece 321 and the like over substantially the entire surface, butis exposed from the connection portion 323 and the core piece 321. Inother words, the outer surface 363 of the rotor magnet 322 is a portionof the outer surface of the rotor main body 32.

In the following description, among the surface of the rotor magnet 322,a region covered by the connection portion 323 is referred to as an“engagement region 371”, and a region exposed from the connectionportion 323 is referred to as an “exposed region 372”. The engagementregion 371 includes a side surface inner end region 365 of an upper endsurface 351, a lower end surface 352, an inner surface 361, and sidesurfaces 362 on both ends of the rotor magnet 322. The exposed region372 includes the outer surface 363 of the rotor magnet 322.

The upper end surface 351 of the rotor magnet 322 includes a firstregion 353 and a second region 354. The first region 353 is positionedinward in the radial direction on the upper end surface 351. The innerend of the first region 353 in the radial direction is, for example, theinner end of the upper end surface 351 in the radial direction. Thesecond region 354 is continuous with the outer end of the first region353 in the radial direction. The second region 354 extends outward inthe radial direction from the outer end of the first region 353 in theradial direction. The outer end of the second region 354 in the radialdirection is, for example, the outer end of the upper end surface 351 inthe radial direction. The outer end of the second region 354 in theradial direction is an end positioned on the side opposite to the firstregion 353 in the second region 354. The radial outer end of the secondregion 354 may be positioned inward in the radial direction of the outerend of the upper end surface 351 in the radial direction.

The outer end of the second region 354 in the radial direction ispositioned below the first region 353. In other words, the outer end ofthe second region 354 in the radial direction is closer to the lower endsurface 352 of the rotor magnet 322 than the first region 353. Thesecond region 354 approaches the lower end surface 352 of the rotormagnet 322 as the second region moves away from the outer end of thefirst region 353 in the radial direction. In an example illustrated inFIG. 6, the second region 354 is an inclined surface which graduallyapproaches the lower end surface 352 in the up and down direction as thesecond region moves away from the first region 353 outward in the radialdirection. The second region 354 is a flat surface in which theinclination angle with respect to the horizontal plane is substantiallyconstant over substantially the entire length in the radial direction.In addition, the first region 353 is a plane substantially vertical tothe up and down direction.

In FIG. 6, a normal vector 355 of the second region 354 is indicated bythick arrow. The normal vector 355 of the second region 354 has acomponent facing outward in the radial direction. In other words, thesecond region 354 is positioned at the same position in the up and downdirection as a portion covering the second region 354 of the connectionportion 323, and faces in the radial direction. In other words, thesecond region 354 of the upper end surface 351 is an engagement surfacethat engages in the radial direction with a portion of the connectionportion 323 covering the second region 354.

Similarly to the upper end surface 351, the lower end surface 352 of therotor magnet 322 includes a first region 356 and a second region 357.The first region 356 is positioned inward in the radial direction on thelower end surface 352. The inner end of the first region 356 in theradial direction is, for example, the inner end of the lower end surface352 in the radial direction. The second region 357 is continuous withthe outer end of the first region 356 in the radial direction. Thesecond region 357 extends outward in the radial direction from the outerend of the first region 356 in the radial direction. The outer end ofthe second region 357 in the radial direction is, for example, an outerend of the lower end surface 352 in the radial direction. The outer endof the second region 357 in the radial direction is an end positioned onthe side opposite to the first region 356 in the second region 357. Theouter end of the second region 357 in the radial direction may bepositioned inward in the radial direction of the outer end of the lowerend surface 352 in the radial direction.

The outer end of the second region 357 in the radial direction ispositioned above the first region 356. In other words, the outer end ofthe second region 357 in the radial direction is closer to the upper endsurface 351 of the rotor magnet 322 than the first region 356. Thesecond region 357 approaches the upper end surface 351 of the rotormagnet 322 as the second region moves away from the outer end of thefirst region 356 in the radial direction. In an example illustrated inFIG. 6, the second region 357 is an inclined surface which graduallyapproaches the upper end surface 351 in the up and down direction as thesecond region goes outward in the radial direction from the first region356. The second region 357 is a flat surface in which the inclinationangle with respect to the horizontal plane is substantially constantover almost the entire length in the radial direction. In addition, thefirst region 356 is a flat surface substantially perpendicular in the upand down direction.

In FIG. 6, a normal vector 358 of the second region 357 is indicated bythick arrow. The normal vector 358 of the second region 357 has acomponent facing outward in the radial direction. In other words, thesecond region 357 is positioned at the same position in the up and downdirection as a portion covering the second region 357 of the connectionportion 323, and faces the portion in the radial direction. In otherwords, the second region 357 of the lower end surface 352 is anengagement surface that engages in a radial direction with a portion ofthe connection portion 323 covering the second region 357.

FIG. 8 is a view illustrating a flow of manufacturing the rotor assembly30. FIG. 9 is a transverse sectional view illustrating the rotorassembly 30 in the process of manufacture. FIG. 10 is a longitudinalsectional view illustrating a portion of the rotor assembly 30 in theprocess of manufacture. In FIGS. 9 and 10, the metal mold 91 used formanufacturing the rotor assembly 30 is also illustrated. FIG. 9illustrates the state before Step S14 is completed after steps S11 toS13 to be described below are completed. FIG. 10 illustrates a statewhere step S14 is being performed.

When the rotor assembly 30 is manufactured, first, the shaft 31 made ofa non-magnetic material is disposed at the center of a substantiallycylindrical magnetic metal mold 91 (step S11). The inner surface 92 ofthe metal mold 91 is a substantially cylindrical surface which has thecentral axis as a center. The central axis of the inner surface 92 ofthe metal mold 91 coincides with the central axis J1 of the motor 1described above.

Subsequently, the plurality of core pieces 321 are arranged in thecircumferential direction around the shaft 31 in the metal mold 91 (stepS12). For example, the plurality of core pieces 321 are handled in astate where the upper end surface and the lower end surface areconnected by the connection plate portion 33 (see FIG. 5). In step S12,the plurality of core pieces 321 are disposed away from the shaft 31outward in the radial direction. In addition, the outer surface 325 ofthe plurality of core pieces 321 abuts against the inner surface 92 ofthe metal mold 91.

Next, the plurality of rotor magnets 322 are alternately arranged in thecircumferential direction with the plurality of core pieces 321 aroundthe shaft 31 in the metal mold 91 (step S13). In step S13, the pluralityof rotor magnets 322 are disposed away from the shaft 31 outward in theradial direction. In addition, the outer surfaces 363 of the pluralityof rotor magnets 322 abut against the inner surface 92 of the metal mold91. As illustrated in FIG. 9, the inner ends of the plurality of rotormagnets 322 in the radial direction are closer to the shaft 31 than theinner ends of the plurality of core pieces 321 in the radial direction.In addition, the first regions 353 and 356 (see FIG. 6) of the upper endsurface 351 and the lower end surface 352 of each rotor magnet 322 arepositioned substantially at the same positions in the up and downdirection with the end surfaces of the upper and lower connection plateportions 33.

In steps S12 and S13, a plurality of rotor magnets 322 and a pluralityof core pieces 321 alternately arranged in the circumferential directionare coupled by the magnetic force of the rotor magnet 322. In addition,the outer surface 363 of the plurality of rotor magnets 322 and theouter surface 325 of the plurality of core pieces 321 are attracted toand abut against the inner surface 92 of the metal mold 91 by themagnetic force of the rotor magnet 322. Step S13 may be performed beforestep S12. Alternatively, step S12 and step S13 may be performed inparallel.

When steps S11 to S13 are completed, as illustrated in FIG. 10, theresin 95 is poured into the metal mold 91 from a plurality of gates 94provided on the upper portion of the metal mold 91. The gate 94 facesthe connection plate portion 33 and the core piece 321 illustrated onthe left side in FIG. 10 and the rotor magnet 322 illustrated on theright side of FIG. 10 in the up and down direction via a gap. The resin95 poured into the metal mold 91 from the gate 94 is filled in a space93 between the shaft 31 and the plurality of core pieces 321 and theplurality of rotor magnets 322. The connection portion 323 is formed byhardening the resin 95, and the shaft 31, the plurality of core pieces321, and the plurality of rotor magnets 322 are connected by theconnection portion 323 (step S14). In addition, the connection portion323 also covers both upper end surfaces of the plurality of core pieces321 and the plurality of rotor magnets 322 in the up and down direction,and the connection plate portion 33. Then, when the metal mold 91 isremoved, the manufacture of the rotor assembly 30 is completed. In stepS14, in a case where there is a gap between the core piece 321 and therotor magnet 322 that are adjacent in the circumferential direction, thegap may also be filled with resin.

In the example illustrated in FIG. 4, the rotor fan 34 is fixed to theshaft 31 on the upper side of the rotor main body 32. The first bearing41 is positioned above the rotor fan 34. In other words, the rotor fan34 is positioned between the first bearing 41 and the rotor main body 32in the up and down direction. The rotor fan 34 faces the first bearing41 and the rotor main body 32 in the up and down direction. The outerdiameter of the rotor fan 34 is larger than the outer diameter of thefirst bearing 41 and larger than the outer diameter of the lower endportion of the bearing holding portion 214. In addition, the outerdiameter of the rotor fan 34 is substantially equal to the outerdiameter of the rotor main body 32. The outer diameter of the rotor fan34 is twice the distance between an outermost edge of a blade 342(described below) and the central axis J1 of the rotor fan 34 in theradial direction.

The rotor fan 34 is a substantially annular member surrounding theperiphery of the shaft 31. The rotor fan 34 is, for example, a diagonalflow fan or a centrifugal fan. The rotor fan 34 includes a fan baseportion 341 and a plurality of blades 342. The fan base portion 341 is asubstantially annular portion which has the central axis J1 as a center.The fan base portion 341 is connected to the outer surface of the shaft31 by press fitting or the like. The plurality of blades 342 areconnected to the fan base portion 341. The plurality of blades 342 arearranged at substantially equal angular intervals in the circumferentialdirection.

The armature 22 faces the rotor main body 32 in the radial direction.The armature 22 includes a core back portion 221, a plurality of teeth222, an insulator 223, and a plurality of coils 224. The core backportion 221 is a substantially cylindrical portion which has the centralaxis J1 as a center. The core back portion 221 is fixed to the innersurface of the side wall portion 211 of the housing 21. The plurality ofteeth 222 extend radially inward from the core back portion 221 in theradial direction. The plurality of teeth 222 are arranged atsubstantially equal angular intervals in the circumferential direction.The core back portion 221 and the plurality of teeth 222 are, forexample, members made of magnetic metal which are connected. Theinsulator 223 is an insulating body covering the surfaces of theplurality of teeth 222. The plurality of coils 224 are formed by windinga conductive wire from above the insulator 223 to the plurality of teeth222. In the present embodiment, the plurality of coils 224 arethree-phase coils.

The plurality of coils 224 are electrically connected to a plurality ofbus bars 23 arranged above the armature 22. In the example illustratedin FIG. 4, the number of bus bars 23 is three. Each bus bar 23 is aconductive member. Each bus bar 23 is a substantially annular orsubstantially arcuate member which has the central axis J1 as a center.The plurality of bus bars 23 include a U-phase bus bar, a V-phase busbar, and a W-phase bus bar. The U-phase bus bar connects the pluralityof U-phase coils 224 among the plurality of coils 224 to each other. TheV-phase bus bar connects the plurality of V-phase coils 224 among theplurality of coils 224 to each other. The W phase bus bar connects theplurality of W phase coils 224 among the plurality of coils 224 to eachother. The plurality of bus bars 23 electrically connect the pluralityof coils 224 of the armature 22 to an external power supply (notillustrated).

The plurality of bus bars 23 are held by the bus bar holding portion 24.The bus bar holding portion 24 is a substantially cylindrical memberwhich has the central axis J1 as a center. The bus bar holding portion24 is an insulating member. The bus bar holding portion 24 is arrangedon the upper side of the armature 22 and faces the armature 22 in the upand down direction. In addition, the bus bar holding portion 24 isdisposed outward of the rotor fan 34 in the radial direction and facesthe rotor fan 34 in the radial direction. The bus bar holding portion 24is fixed to the housing 21 or the armature 22, for example.

The bus bar holding portion 24 includes an inner cylindrical portion241, a flange portion 242, and an outer cylindrical portion 243. Theinner cylindrical portion 241 is a substantially cylindrical portionwhich has the central axis J1 as a center. The flange portion 242 is asubstantially annular portion extending outward from the lower endportion of the inner cylindrical portion 241 in the radial direction. Inthe example illustrated in FIG. 4, the flange portion 242 faces downwardas the flange portion goes outward in the radial direction. The outercylindrical portion 243 faces downward from the outer end portion of theflange portion 242. The outer cylindrical portion 243 is a substantiallycylindrical portion about the central axis J1. The inner cylindricalportion 241, the flange portion 242, and the outer cylindrical portion243 are, for example, members made of resin which are connected.

In the bus bar holding portion 24, the outer surface of the outercylindrical portion 243 comes in contact with the inner surface of theside wall portion 211 of the housing 21. The lower end portion of theouter cylindrical portion 243 comes in contact with the upper endportion of the core back portion 221 of the armature 22. The flangeportion 242 is provided with a plurality of groove portions 244 openingupward. Each of the groove portions 244 is substantially annular orsubstantially arcuate which has the central axis J1 as a center. In eachgroove portion 244, the bus bar 23 is accommodated and fixed. In theexample illustrated in FIG. 4, three bus bars 23 are fixed to the threegroove portions 244 of the bus bar holding portion 24. The number of thebus bars 23 held by the bus bar holding portion 24 may be 1, or 2 ormore. In addition, the bus bar 23 in the groove portion 244 may bemolded with resin.

The bus bar holding portion 24 is a substantially cylindrical windtunnel portion disposed outside the rotor fan 34 in the radialdirection. The inner surface 245 of the inner cylindrical portion 241 ofthe bus bar holding portion 24 is substantially cylindrical which hasthe central axis J1 as a center. The inner surface 245 of the bus barholding portion 24 faces the rotor fan 34 in the radial direction. Theinner surface 245 of the bus bar holding portion 24 is positionedoutward in the radial direction the outer edge of each blade 342 of therotor fan 34 in the radial direction and is close to the outer edge ofeach blade 342 in the radial direction. The inner surface 245 of the busbar holding portion 24 faces each blade 342 in the radial direction oversubstantially the entire length of each blade 342 in the up and downdirection. The upper end of the inner surface 245 of the bus bar holdingportion 24 is positioned above the upper ends of each blade 342 of therotor fan 34.

The upper end portion of the inner surface 245 of the bus bar holdingportion 24 faces the outer surface 217 of the bearing holding portion214 in the radial direction. The outer surface 217 of the bearingholding portion 214 is an inclined surface that faces inward in theradial direction as outer surface goes downward. The outer surface 217of the bearing holding portion 214 is, for example, a side surface of asubstantially truncated cone. The outer surface 217 of the bearingholding portion 214 is positioned at substantially the same position inthe up and down direction as each first opening 215 of the housing 21.In other words, each of the first openings 215 faces the outer surface217 of the bearing holding portion 214 in the radial direction.

The lower surface 246 of the flange portion 242 of the bus bar holdingportion 24 is a substantially annular surface which has the central axisJ1 as a center. The lower surface 246 of the flange portion 242 extendsoutward from the lower end of the inner surface 245 of the innercylindrical portion 241 in the radial direction. The lower surface 246of the flange portion 242 is an inclined surface facing downward as thelower surface thereof faces outward from the lower end of the innersurface 245 in the radial direction. The lower surface 246 of the flangeportion 242 is positioned between the armature 22 and the bus bar 23which are arranged in the up and down direction. The lower surface 246of the flange portion 242 faces the armature 22 in the up and downdirection.

In the motor 1, a current is supplied to the coil 224 of the armature 22via the bus bar 23, so that a torque is generated between the coil 224and the rotor main body 32. Accordingly, the rotation portion 3, thatis, the rotor assembly 30 and the rotor fan 34 rotate about the centralaxis J1 in the circumferential direction.

In the motor 1, when the plurality of blades 342 of the rotor fan 34rotate in the circumferential direction, the flow of the air from thefirst opening 215 to the second opening 216 via the armature 22 andvicinity thereof is formed in the motor 1. In the motor 1, by rotatingthe rotor fan 34 in the direction opposite to the above, the flow of theair from the second opening 216 to the first opening 215 via thearmature 22 and vicinity thereof may be formed in the motor 1. In eithercase, due to the air flow, the internal structure of the motor 1, inparticular the armature 22, is cooled.

Hereinafter, the cooling by the rotor fan 34 will be described morespecifically. In the motor 1, as the plurality of blades 342 of therotor fan 34 rotate in the counterclockwise direction in the plan view,the air above the rotor fan 34 flows downward, and flows into theinterior of the inner cylindrical portion 241 via the upper end openingin the inner cylindrical portion 241 of the bus bar holding portion 24.As a result, the air outside the housing 21 flows into the housing 21via the plurality of first openings 215, and flows downward toward therotor fan 34 rotating inside the inner cylindrical portion 241.

The inner cylindrical portion 241 rectifies the flow of air flowing intothe rotor fan 34 and the flow of air sent out from the rotor fan 34 in adirection parallel to the central axis J1. Accordingly, the blowingefficiency by the rotor fan 34 can be improved. The air that passesthrough the inner cylindrical portion 241 and flows out downward fromthe lower end opening of the inner cylindrical portion 241 expandsoutward in the radial direction along the lower surface 246 of theflange portion 242 and the outer surface of the central protrusionportion 326 of the connection portion 323 and flows downward toward thearmature 22. The air passes downward through the gap between the coil224 of the armature 22 and the gap between the armature 22 and the rotormain body 32, flows downward, and flows out of the housing 21 via theplurality of second openings 216.

Accordingly, as described above, a flow of air from the first opening215 to the second opening 216 via the armature 22 and the vicinitythereof is formed inside the motor 1. As a result, the internalstructure of the motor 1, particularly the armature 22, is cooled. Thefirst opening 215 is an inlet through which air flows into the interiorof the motor 1 and the second opening 216 is an outlet through which airinside the motor 1 flows out.

On the other hand, in a case where the plurality of blades 342 of therotor fan 34 rotate in the clockwise direction in the plan view, a flowof air from the second opening 216 to the first opening 215 via thearmature 22 and the vicinity thereof is formed in the motor 1. As aresult, the internal structure of the motor 1, particularly the armature22, is cooled in the same manner as described above. In this case, thesecond opening 216 is an inlet through which air flows into the motor 1,and the first opening 215 is an outlet through which air inside themotor 1 flows out.

As described above, the rotor assembly 30 includes the shaft 31 and thecylindrical rotor main body 32. The shaft 31 has the central axis J1along the up and down direction as a center. The rotor main body 32 isfixed to the outer surface of the shaft 31. The rotor main body 32includes the plurality of core pieces 321, the plurality of rotormagnets 322, and the connection portion 323 which is made of resin. Theplurality of core pieces 321 are arranged around the shaft 31 in thecircumferential direction. The plurality of rotor magnets 322 arearranged alternately with the plurality of core pieces 321 around theshaft 31 in the circumferential direction. The connection portion 323connects the shaft 31 to the plurality of core pieces 321 and theplurality of rotor magnets 322.

Each rotor magnet 322 includes an engagement region 371 and an exposedregion 372. The engagement region 371 is a region covered by theconnection portion 323 on the surface of the rotor magnet 322. Theexposed region 372 is a region of the surface of the rotor magnet 322exposed from the connection portion 323. The exposed region 372 includesan outer surface 363 positioned outward in the radial direction. Theengagement region 371 includes an engagement surface having a componentwhose normal vector faces outward in the radial direction.

In the rotor assembly 30, the engagement surface engages with a portionof the connection portion 323 covering the engagement surface in theradial direction, whereby the outward movement of the rotor magnet 322in the radial direction is restricted. As a result, the movement of therotor magnet 322 outward in the radial direction due to the centrifugalforce acting when the rotor assembly 30 rotates can be suppressed. Inaddition, since the outer surface 363 of the rotor magnet 322 is notcovered by the connection portion 323, the increase in the size of therotor assembly 30 in the radial direction can be suppressed. In otherwords, in the rotor assembly 30 described above, the outward movement ofthe rotor magnet 322 in the radial direction can be suppressed whilesuppressing the increase in the size of the rotor assembly 30.

In the motor 1, as described above, since the outer surface 363 of therotor magnet 322 is not covered by the connection portion 323, thedistance between the outer surface 363 of the rotor magnet 322 and thearmature 22 in the radial direction can be reduced. Accordingly, theleakage magnetic flux from the rotor magnet 322 can be reduced and theoutput of the motor 1 can increase.

As described above, the upper end surface 351 of each rotor magnet 322includes a first region 353 positioned inward in the radial directionand a second region 354 extending from the outer end of the first region353 in the radial direction. The second region 354 approaches the lowerend surface 352 of each rotor magnet 322 as the second region moves awayfrom the outer end of the first region 353 in the radial direction. Theengagement surface of the engagement region 371 includes the secondregion 354. Accordingly, the engagement surface as described above canbe easily formed.

In addition, the lower end surface 352 of each rotor magnet 322 includesa first region 356 positioned inward in the radial direction and asecond region 357 extending from the outer end of the first region 356in the radial direction. The second region 357 approaches the upper endsurface 351 of each rotor magnet 322 as the second region moves awayfrom the outer end of the first region 356 in the radial direction. Theengagement surface of the engagement region 371 further includes thesecond region 357. Accordingly, the engagement surface of the engagementregion 371 can be easily formed, and the outward movement of the rotormagnet 322 in the radial direction can be further suppressed.

In the rotor assembly 30, the second region described above may beprovided only on one end surface of the upper end surface 351 and thelower end surface 352 of each rotor magnet 322. In other words, one endsurface of each rotor magnet 322 in the up and down direction includes afirst region positioned inward in the radial direction and a secondregion extending from the outer end of the first region in the radialdirection. The second region approaches the other end surface of eachrotor magnet 322 in the up and down direction as the second region movesaway from the outer end of the first region in the radial direction. Theengagement surface of the engagement region 371 includes the secondregion. Accordingly, similarly to the above, formation of the engagementsurface can be facilitated. As a result, the outward movement of therotor magnet 322 in the radial direction can be suppressed by a simplestructure.

In addition, the second region is an inclined surface that graduallyapproaches the other end surface in the up and down direction as thesecond region moves away from the first region outward in the radialdirection. Accordingly, the rotor magnet 322 is formed by providing anotch including the second region in the substantially parallelepipedmagnet, as compared with a case where the second region is a surfaceperpendicular in the radial direction, a decrease in the volume of therotor magnet 322 by formation of the second region can be suppressed. Asa result, reduction in output of the motor 1 can be suppressed.

As described above, each core piece 321 includes a core recessed portion324 recessed outward in each radial direction on an inner surface of thesurface of each core piece 321 located inward in the radial direction.The inner surface of each core piece 321 is covered by a connectionportion 323. In the core recessed portion 324, the resin of theconnection portion 323 is provided. Accordingly, the contact areabetween each core piece 321 and the connection portion 323 can increase.As a result, the movement of the core piece 321 outward in the radialdirection due to the centrifugal force acting when the rotor assembly 30rotates can be suppressed. In addition, the maximum width of the corerecessed portion 324 in the circumferential direction is greater thanthe width of the core recessed portion 324 in the circumferentialdirection on the inner surface of the core piece 321. Accordingly, sincethe resin in the core recessed portion 324 acts as a so-called wedge,the outward movement of the core piece 321 in the radial direction canbe further suppressed.

As described above, the rotor assembly 30 further includes a plate-likeconnection plate portion 33. The connection plate portion 33 is disposedon an end portion of the rotor main body 32 in the up and downdirection, and connects the rotor main body 32 and the shaft 31. Theconnection plate portion 33 includes an annular first portion 331 and aplurality of second portions 332. The first portion 331 is connected tothe outer surface of the shaft 31. The plurality of second portions 332extend outward from the first portion 331 in the radial direction. Theplurality of second portions 332 are overlapped with the plurality ofcore pieces 321 in the up and down direction and are connected to theplurality of core pieces 321. Accordingly, the outward movement of theplurality of core pieces 321 can be suppressed in the radial direction.In addition, since the plurality of core pieces 321 can be handledintegrally, manufacturing of the rotor assembly 30 and the motor 1 canbe facilitated.

FIG. 11 is an enlarged longitudinal sectional view illustrating anotherpreferred rotor magnet 322 a and vicinity thereof. In each rotor magnet322 a, the upper end surface 351 includes the first region 353 describedabove, a second region 354 a having a different shape from the secondregion 354 described above, and a third region 353 a. The second region354 a is a plane substantially parallel in the up and down direction andsubstantially perpendicular in the radial direction. A normal vector 355a of the second region 354 a is substantially parallel in the radialdirection and faces outward in the radial direction. The second region354 a approaches the lower end surface 352 of the rotor magnet 322 a asthe second region moves away in the up and down direction from the outerend of the first region 353 in the radial direction. In the engagementregion 371 on the surface of the rotor magnet 322 a, the second region354 a is included in the engagement surface having a component whosenormal vector 355 faces outward in the radial direction. The thirdregion 353 a extends outward from the lower end of the second region 354a in the radial direction. The third region 353 a is a surface that issubstantially perpendicular in the up and down direction. On the upperend surface 351 of the rotor magnet 322 a, a stepped portion formed bythe first region 353, the second region 354 a, and the third region 353a is provided.

In addition, in each rotor magnet 322 a, the lower end surface 352includes the first region 356 described above, a second region 357 ahaving a different shape from the second region 357 described above, anda third region 356 a. The second region 357 a is a plane substantiallyparallel in the up and down direction and substantially perpendicular inthe radial direction. A normal vector 358 a of the second region 357 ais substantially parallel in the radial direction and faces outward inthe radial direction. The second region 357 a approaches the upper endsurface 351 of the rotor magnet 322 a as the second region moves awayfrom the outer end of the first region 356 in the radial direction, inthe up and down direction. In the engagement region 371 on the surfaceof the rotor magnet 322 a, the second region 357 a is included in theengagement surface having a component whose normal vector 358 facesoutward in the radial direction. The third region 356 a extends outwardfrom the lower end of the second region 357 a in the radial direction.The third region 356 a is a surface that is substantially perpendicularin the up and down direction. On the lower end surface 352 of the rotormagnet 322 a, a stepped portion formed by the first region 356, thesecond region 357 a, and the third region 356 a is provided.

In the rotor assembly 30 a including the rotor magnet 322 a, similarlyto the rotor assembly 30 described above, the engagement region 371 ofeach rotor magnet 322 a includes an engagement surface having acomponent whose normal vector faces outward in the radial direction.Accordingly, the outward movement of the rotor magnet 322 a in theradial direction can be suppressed while suppressing the increase insize of the rotor assembly 30 a.

In the rotor assembly 30 a, the second region described above may beprovided only on one end surface of the upper end surface 351 and thelower end surface 352 of each rotor magnet 322 a. In other words, oneend surface of each rotor magnet 322 a in the up and down directionincludes a first region positioned inward in the radial direction and asecond region extending from the outer end of the first region in theradial direction. The second region approaches the other end surface ofeach rotor magnet 322 a in the up and down direction as the secondregion moves away from the outer end of the first region in the radialdirection. The engagement surface of the engagement region 371 includesthe second region. Accordingly, similarly to the above, formation of theengagement surface can be facilitated. As a result, the outward movementof the rotor magnet 322 a in the radial direction can be suppressed by asimple structure.

In the rotor magnet 322 a, for example, a plurality of stepped portionseach having substantially the same structure as that of the steppedportion described above may be provided in a substantially stepped shapecontinuously in the radial direction on the upper end surface 351. Aplurality of stepped portions having substantially stepped shapes mayalso be provided on the lower end surface 352.

In addition, in the rotor assembly 30 a, for example, each secondportion 332 (see FIG. 5) of the connection plate portion 33 describedabove extends in the circumferential direction, and a portion of eachsecond portion 332 extending in the circumferential direction mayoverlap the third regions 353 a and 356 a of the adjacent rotor magnet322 a in the up and down direction. A portion extending of each secondportion 332 in the circumferential direction comes in contact with thethird regions 353 a and 356 a and faces the second regions 354 a and 357a in the radial direction. Accordingly, the outward movement of therotor magnet 322 a in the radial direction can be suppressed.

FIG. 12 is an enlarged transverse sectional view illustrating anotherpreferred rotor magnet 322 b and vicinity thereof. In each rotor magnet322 b, the side inner end regions 365 of the side surfaces 362 in thecircumferential direction include a fourth region 366 extending from theside surface 362 toward the interior of the rotor magnet 322 b. In otherwords, the fourth region 366 disposed on one side surface 362 extendsfrom the region around the fourth region 366 in a direction approachingthe other side surface 362. Accordingly, a recessed portion is formed inthe side inner end region 365 of the rotor magnet 322 b. The recessedportion is provided, for example, over substantially the entire lengthof the rotor magnet 322 b in the up and down direction. In the exampleillustrated in FIG. 12, the fourth region 366 is an inclined surfacegradually approaching the other side surface 362 as going outward in theradial direction. The fourth region 366 may be, for example, a flatsurface substantially perpendicular in the radial direction.

In the rotor assembly 30 b including the rotor magnet 322 b, similarlyto the rotor assembly 30 described above, the engagement region 371 ofeach rotor magnet 322 b includes the fourth region 366 which is anengagement surface having a component whose normal vector 367 facesoutward in the radial direction. In the rotor assembly 30 b, by coveringthe fourth region 366 by the connection portion 323, the outwardmovement of the rotor magnet 322 b in the radial direction can besuppressed while suppressing the increase in size of the rotor assembly30 b.

FIG. 13 is an enlarged transverse sectional view illustrating a rotormagnet 322 c and a portion in the vicinity thereof in a rotor assembly30 c according to another embodiment of the present disclosure. In therotor assembly 30 c, the structure of the rotor magnet 322 c ispartially different from the structure of the rotor magnet 322 of therotor assembly 30 described above. Other configurations of the rotorassembly 30 c are substantially the same as those of the rotor assembly30 illustrated in FIGS. 2 to 7. In the following description, the samereference numeral is given to the configuration of the rotor assembly 30c corresponding to each configuration of the rotor assembly 30.

In the rotor assembly 30 c, a recessed portion 368 and a protrusionportion are provided in the inner surface 361 of the rotor magnet 322 cand the side inner end region 365 of both side surfaces 362 in thecircumferential directions. The protrusion portion is a portion otherthan the recessed portion 368. In the following description, therecessed portion 368 will be referred to as “magnet recessed portion368”. In an example illustrated in FIG. 13, the magnet recessed portion368 is a large number of minute recessed portions 369 formed by thesurface treatment on the rotor magnet 322 c. The surface treatment is,for example, a chemical conversion treatment, a laser treatment, or asandblast treatment. The depth of each minute recessed portion 369 is,for example, about 1 μm. In FIG. 13, the minute recessed portion 369 isdrawn larger than it actually is. In the large number of minute recessedportions 369, the resin of the connection portion 323 continuouslyenters from the periphery of the minute recessed portion 369. In otherwords, a portion of the connection portion 323 formed of a resin isprovided in a large number of minute recessed portions 369.

Like the rotor assembly 30 illustrated in FIGS. 2 to 6, the rotorassembly 30 c includes a shaft 31 and a cylindrical rotor main body 32.The shaft 31 has the central axis J1 along the up and down as a center.The rotor main body 32 is fixed to the outer surface of the shaft 31. Asillustrated in FIG. 13, the rotor main body 32 includes a plurality ofcore pieces 321, a plurality of rotor magnets 322 c, and a resinconnection portion 323. The plurality of core pieces 321 are arrangedaround the shaft 31 in the circumferential direction. The plurality ofrotor magnets 322 c are arranged alternately with the plurality of corepieces 321 around the shaft 31 in the circumferential direction. Theconnection portion 323 connects the shaft 31, the plurality of corepieces 321, and the plurality of rotor magnets 322 c.

Each rotor magnet 322 c includes an engagement region 371 and an exposedregion 372. The engagement region 371 is a region covered by theconnection portion 323 on the surface of the rotor magnet 322 c. Theexposed region 372 is a region exposed from the connection portion 323on the surface of the rotor magnet 322 c. The exposed region 372includes an outer surface 363 positioned outward in the radialdirection. The engagement region 371 includes a magnet recessed portion368 and a protrusion portion.

In the rotor assembly 30 c, since the resin of the connection portion323 is provided in the magnet recessed portion 368, the contact area ofthe connection portion 323 with the rotor magnet 322 c increases.Accordingly, the outward movement of the rotor magnet 322 c due to thecentrifugal force acting when the rotor assembly 30 c rotates can besuppressed. In addition, since the outer surface 363 of the rotor magnet322 c is not covered by the connection portion 323, the increase in thesize of the rotor assembly 30 c in the radial direction. In other words,in the above-described rotor assembly 30 c, the outward movement of therotor magnet 322 c in the radial direction can be suppressed while theincrease in the size of the rotor assembly 30 c.

As described above, in the rotor assembly 30 c, the magnet recessedportion 368 of the engagement region 371 is a large number of minuterecessed portions 369 formed by the surface treatment of each rotormagnet 322 c. Accordingly, a decrease in the volume of the rotor magnet322 c due to the formation of the magnet recessed portion 368 can besuppressed. As a result, reduction in output of the motor including therotor assembly 30 c can be suppressed.

In the rotor assembly 30 c, each core piece 321 includes a core recessedportion 324 recessed outward in the radial direction on an inner surfacepositioned inward of the surface of each core piece 321 in the radialdirection. The inner surface of each core piece 321 is covered by aconnection portion 323. In the core recessed portion 324, the resin ofthe connection portion 323 is provided. Accordingly, the contact areabetween each core piece 321 and the connection portion 323 can increase.As a result, the moment of the core piece 321 outward in the radialdirection due to the centrifugal force acting when the rotor assembly 30c rotates can be suppressed. In addition, the maximum width of the corerecessed portion 324 in the circumferential direction is greater thanthe width of the core recessed portion 324 in the circumferentialdirection on the inner surface of the core piece 321. Accordingly, theoutward movement of the core piece 321 in the radial direction can befurther suppressed.

The rotor assembly 30 c further includes the connection plate portion 33having a plate shape illustrated in FIG. 5. The connection plate portion33 is disposed at an end portion of the rotor main body 32 in the up anddown direction, and connects the rotor main body 32 and the shaft 31.The connection plate portion 33 includes an annular first portion 331and a plurality of second portions 332. The first portion 331 isconnected to the outer surface of the shaft 31. The plurality of secondportions 332 extend outward from the first portion 331 in the radialdirection. The plurality of second portions 332 are overlapped with theplurality of core pieces 321 in the up and down direction and areconnected to the plurality of core pieces 321. Accordingly, the outwardmovement of the plurality of core pieces 321 in the radial direction canbe supplied. In addition, since the plurality of core pieces 321 can behandled integrally, the rotor assembly 30 c and the motor can be easilymanufactured.

In the rotor magnet 322 c, the large number of minute recessed portions369 which are the magnet recessed portions 368 are not necessarilyprovided in the inner surface 361 and both side inner end regions 365 inthe circumferential direction. For example, the large number of minuterecessed portions 369 may be provided only on the inner surface 361, ormay be provided only on one side inner end region 365 in thecircumferential direction. Alternatively, the plurality of minuterecessed portions 369 may be provided on one or both end surfaces of theupper end surface 351 of the lower end surface 352 (see FIG. 6) of therotor magnet 322 c.

The magnet recessed portion 368 described above is not necessarily alarge number of minute recessed portions 369, and in the rotor magnet322 c, one, or two or more magnet recessed portions 368 may be providedin the engagement region 371. In addition, the magnet recessed portions368 may be provided in the rotor assemblies 30, 30 a, and 30 c in whichthe engagement surface described above is included in the engagementregion 371.

Various modifications are possible in the rotor assembly 30, 30 a to 30c, and the motor 1 described above.

For example, in each rotor magnet 322 of the rotor assembly 30, thefirst region 353 is omitted from the upper end surface 351, and thesecond region 354 as the engagement surface may extend outward in theradial direction from the inner end of the upper end surface 351 in theradial direction. In addition, the first region 356 may be omitted fromthe lower end surface 352 and the second region 357 as the engagementsurface may extend outward in the radial direction from the inner end ofthe lower end surface 352 in the radial direction.

In the rotor assembly 30, the core recessed portion 324 may be omittedfrom the inner surface of each core piece 321. In addition, in the rotorassembly 30, the connection plate portion 33 may also be omitted. Thesame applies to the rotor assemblies 30 a to 30 c.

In the rotor assembly 30, the outer surfaces 325 of the plurality ofcore pieces 321 and the outer surfaces 363 of the plurality of rotormagnets 322 are not necessarily required to be positioned at the samepositions in the radial direction, and one outer surface may bepositioned outward the other outer surface in the radial direction. Thesame applies to the rotor assemblies 30 a to 30 c.

In the rotor assembly 30, substantially the entire outer surface 363 ofeach rotor magnet 322 may be exposed from the connection portion 323. Inother words, substantially the entire outer surface 363 may be includedin the exposed region 372. For example, in a case where a chamferingprocess is performed on the side edge portion of the outer surface 363in the circumferential direction, a notch or the like formed by thechamfering process is covered by a resin and the upper and lowerconnection portions 323 of the rotor magnet 322 may be connected by theresin. The same applies to the rotor assemblies 30 a to 30 c.

In the rotor assembly 30, the inner ends of the plurality of rotormagnets 322 in the radial direction may be positioned at the samepositions in the radial direction with the inner ends of the pluralityof core pieces 321 in the radial direction. Alternatively, the radialinner ends of the plurality of rotor magnets 322 may be further awayfrom the shaft 31 than the inner ends of the plurality of core pieces321 in the radial direction. The same also applies to the rotor assembly30 a.

The position of the first opening 215 may be appropriately changed onthe upper side of the armature 22. For example, the first opening 215may be disposed in the canopy portion 213 of the housing 21 instead ofthe side wall portion 211 of the housing 21. The position of the secondopening 216 may be appropriately changed on the lower side than thearmature 22. For example, the second opening 216 may be disposed in theside wall portion 211 of the housing 21 instead of the bottom portion212 of the housing 21.

The shape, structure and material of each configuration of the motor 1may be variously changed. For example, as illustrated in FIG. 14, therotor fan 34 may be a member connected to the rotor main body 32. In theexample illustrated in FIG. 14, the central protrusion portion 326 ofthe connection portion 323 extends to the vicinity of the first bearing41, and the plurality of blades 342 are connected to the outer surfaceof the central protrusion portion 326, whereby the rotor fan 34 areformed.

The motor 1 is not necessarily limited to a three-phase motor, and maybe various types of motors. The motor 1 may be used for various devicesother than the axial flow fan.

The motor according to the present disclosure can be used as a motor forvarious purposes. The motor is preferably used for an axial flow fan.

Features of the above-described preferred embodiments and themodifications thereof may be combined appropriately as long as noconflict arises.

While preferred embodiments of the present disclosure have beendescribed above, it is to be understood that variations andmodifications will be apparent to those skilled in the art withoutdeparting from the scope and spirit of the present disclosure. The scopeof the present disclosure, therefore, is to be determined solely by thefollowing claims.

What is claimed is:
 1. A rotor assembly comprising: a shaft that has acentral axis extending along an up and down direction as a center; and acylindrical rotor main body that is fixed to an outer surface of theshaft; wherein the rotor main body includes: core pieces arranged aroundthe shaft in a circumferential direction; rotor magnets alternatelyarranged with the core pieces around the shaft in the circumferentialdirection; and a connection portion that is made of resin and connectsthe shaft to the core pieces and the rotor magnets; each of the rotormagnets includes: an engagement region that is covered by the connectionportion; and an exposed region that includes an outer surface positionedoutward of the rotor magnet surface in a radial direction and exposedfrom the connection portion; and the engagement region includes anengagement surface including a component with a normal vector that facesoutward in the radial direction.
 2. The rotor assembly according toclaim 1, wherein a first end surface of each of the rotor magnets in theup and down direction includes: a first region that is positioned inwardin the radial direction; and a second region that extends out from anouter end of the first region in the radial direction; and the secondregion approaches a second end surface of each of the rotor magnets inthe up and down direction as the second region extends away from theouter end of the first region in the radial direction; and theengagement surface of the engagement region includes the second region.3. The rotor assembly according to claim 2, wherein the second regionincludes an inclined surface that approaches the second end surface inthe up and down direction as the second region extends away from thefirst region outward in the radial direction.
 4. The rotor assemblyaccording to claim 1, wherein each of the core pieces includes a corerecessed portion that is recessed outward in the radial direction on aninner surface positioned inward of the surface of each of the corepieces in the radial direction; and the inner surface of each of thecore pieces is covered by the connection portion and the resin of theconnection portion is provided in the core recessed portion.
 5. Therotor assembly according to claim 1, further comprising: a plate-shapedconnection plate portion that is disposed on an end portion of the rotormain body in the up and down direction and connects the rotor main bodyand the shaft; the connection plate portion includes: wherein an annularfirst portion that is connected to the outer surface of the shaft; andsecond portions that are connected to the core pieces by extendingoutward from the first portion in the radial direction and overlappingthe core pieces in the up and down direction.
 6. A rotor assemblycomprising: a shaft that has a central axis along an up and downdirection as a center; and a cylindrical rotor main body that is fixedto an outer surface of the shaft; wherein the rotor main body includes:core pieces arranged around the shaft in a circumferential direction;rotor magnets arranged alternately with the core pieces around the shaftin the circumferential direction; and a connection portion that is madeof resin and connects the shaft to the core pieces and the plurality ofrotor magnets; wherein each of the rotor magnets includes: an engagementregion that is covered by the connection portion of the rotor magnetsurface; and an exposed region that includes an outer surface positionedoutward of the rotor magnet surface in a radial direction and exposedfrom the connection portion; and the engagement region includes arecessed portion and a protrusion portion.
 7. The rotor assemblyaccording to claim 6, wherein the recessed portion of the engagementregion includes recessed portions defined by a surface treatment on eachof the rotor magnets.
 8. The rotor assembly according to claim 6,wherein each of the core pieces includes a core recessed portion that isrecessed outward in the radial direction on an inner surface positionedinward of the surface of each of the core pieces in the radialdirection; and the inner surface of each of the core pieces is coveredby the connection portion and the resin of the connection portion isprovided in the core recessed portion.
 9. The rotor assembly accordingto claim 6, further comprising: a plate-shaped connection plate portionthat is disposed on an end portion of the rotor main body in the up anddown direction and connects the rotor main body and the shaft; whereinthe connection plate portion includes: an annular first portion that isconnected to the outer surface of the shaft; and a plurality of secondportions that are connected to the plurality of core pieces by extendingoutward from the first portion in the radial direction and overlappingthe plurality of core pieces in the up and down direction.
 10. A motorcomprising: the rotor assembly according to claim 1; a bearing mechanismthat rotatably supports the shaft of the rotor assembly; an armaturethat faces the rotor main body of the rotor assembly in the radialdirection; and a housing that accommodates the rotor assembly therein.